1. Field of the Invention
The present invention relates to a broad band, broad beam, low profile ultra-high frequency antenna element, and, more particularly, to such an antenna element having an overall reduced antenna height while achieving a vertically polarized signal above a ground plane and maintaining the antenna gain.
2. Description of Related Art
Notch antennas typically are in the form of a planar arrangement with a pair of conductors flaring away from a common feed point along a so-called "notch". The curve of the two conductors flaring away from one another is typically exponential, but may be other mathematical curves, and the resulting antenna may be constructed to have a wide variation in desirable characteristics. Electromagnetic energy is provided to the base of the notch with appropriate sizing being provided for matching transmission line impedance. As to operation, the conductors flaring away from one another produces a gradual increase of the effective impedance between them until it matches the free space impedance at which time, the antenna conductors act like impedance matching transformers and result in launching of a radio frequency energy wave into the surrounding free space. Construction of such antennas can be desirably accomplished by the use of printed circuit materials which enables combining a large number of the antenna elements into arrays useful for a wide variety of special applications such as, for example, radio astronomy, electronic air defense systems, and radar.
For general background of such antennas, reference is made to the paper entitled "Endfire Slotline Antennas" presented at JINA 1990 Nice, France, 13-15 November by Daniel H. Schaubert. Reference is also made to pending application, Ser. No. 08/158,057 filed Nov. 24, 1993 for RESONATED NOTCH ANTENNA assigned to the same assignee as this present document in which a dipole endfire slot antenna is described.
Although the above-referenced known antennas are satisfactory under many circumstances, it is desirable to be able to achieve additional antenna gain, to reduce the height of the antenna, as well as maintain a vertically polarized antenna above a ground plane.